This invention relates generally to printed circuit boards, and, more particularly, to methods and apparatus for soldering printed circuit boards.
Tin or tin alloy deposits have been widely used in fabricating electronic circuits, electronic devices and electrical connectors because of the benefits that such deposits provide. For example, tin and tin alloy deposits protect the components from corrosion, provide a chemically stable surface for soldering and maintain good surface electrical contact.
At least some known electrical components, such as for example, surface mount components have a plurality of conductive terminals with tin or tin alloy deposit thereon. The terminals of the surface mount components are then placed on a printed circuit board, and are soldered onto the printed circuit board by a known reflow soldering process. However, most portion of the terminals are still exposed in the air after the reflow soldering process, and the tin or tin alloy deposit on the exposed portion have a tendency of whisker shaped formation growing from the outer surface thereof, known as “tin whisker”. Such tin whiskers considerably decrease the operation reliability of the electrical components, and increase the maintenance cost of the equipment utilizing such electrical components. At least some known producers store the wave soldered components for 3000 to 4000 hours for observing the tin whisker situation, which is obviously undesired by the producers.